It is well know that monitoring physiological parameters in situ and in vivo within a blood vessel of a human subject being diagnosed or treated during a medical procedure can provide medical professionals critical information as to the status and condition of the human subject. One particular important and beneficial physiological parameter is the blood pressure within the coronary vessel. Study has shown that the blood pressure in situ and in viva within the coronary vessel can be applied to calculate Fractional Flow Reserve (FFR) which represents the potential decrease in coronary flow distal to the coronary stenosis. More than a decade long clinic study has shown that FFR can provide a quantitative assessment of the functional severity of a coronary artery stenosis identified during coronary angiography and cardiac catheterization, hence, helping the physician to make a quantitative decision on which kind of further treatment is required.
Due to the small diameter of the coronary vessel, which can be as small as less than 1 mm in diameter, it is crucial to have a very small diagnosis device to measure the blood pressure in situ so the blood pressure is not distorted by the diagnosis device itself. In such case, an ultra small pressure sensor is mounted at the distal end of an ultra small delivering device such as a guide wire to form a sensor guide wire assembly. By advancing the distal end of the sensor guide wire assembly to the desired location within the coronary vessel, the ultra miniature pressure sensor mounted at the distal end of the guide wire can perform the measurement of the blood pressure of the coronary vessel in situ and in viva. The Outside Diameter (OD) of the sensor guide wire assembly is typically 0.35 mm. Hence an ultra small sensor is required so the sensor can be mounted at the distal end of the sensor guide wire assembly.
Therefore it is apparent that there is a need to manufacture miniature pressure sensors which can be mounted at the distal end of delivering devices such as guide wires. In order to mount the pressure sensor on a guide wire whose typical Outside Diameter (OD) is about 0.35 mm, the size of the sensor needs to be smaller than 0.3 mm in width and 0.1 mm in height. To fabricate pressure sensors with this small dimension presents a challenge for mass production.